1. Field of the Invention
This invention generally relates to surgical instruments and more specifically to tissue retractors for use in various surgical procedures.
2. Description of Related Art
Surgical retractors are well known in the medical arts, particularly retractors that separate body tissue to enable a surgeon access to an operating site. Generally these retractors include two arms that can pivot about an axis at an intermediate position to form a scissors-like mechanism. Squeezing finger grips at one end of each arm causes a pair of retractor claws at the other ends of each arm to separate. Once the desired tissue separation is achieved, a ratchet sector on one arm and a pawl on the other arm lock the arms in place relative to each other and thereby maintain the tissue separation. The following patents disclose some examples of such retractors:
U.S. Pat. No. 3,038,467 (1962) Sovatkin PA1 U.S. Pat. No. 3,470,872 (1969) Grieshaber PA1 U.S. Pat. No. 3,998,217 (1976) Trumbull et al. discloses another type of retractor device that engages tissue at four different positions. While such an approach provides more tissue contacts, it has not gained wide acceptance. Scissors-type retractors continue to be the instruments of choice.
These retractors, however, only provide separation at two opposed locations. The following patent:
There has also been introduced a variation on a scissors-type retractor whereby a central claw attaches to the retractor to provide three tissue contacts. Specifically, one retractor with this capability includes two retractor arms that can pivot about a pivot axis. Each arm includes a finger grip and a claw at opposite ends. A central claw has an intermediate planar portion with a clearance passage at an intermediate location along an elongated slot. A wing bolt attaches to a threaded receptacle formed in one of the arms along the pivot axis. To attach the central claw, a surgeon grasps the retractor in one hand and uses the other hand to loosen the wing bolt. Then the surgeon aligns the clearance passage with the wing bolt so that the central claw passes over the wing bolt. The surgeon must then displace the central claw so that a flange on the wing bolt overlies portions of the central claw to capture it. Next the surgeon positions the central claw against a patient's tissue and then tightens the wing bolt to effect clamping solely by generating frictional forces between smooth facing surfaces of the wing bolt flange and the central claw.
This arrangement does advantageously increase the number of tissue contact points. However, if it becomes necessary to reset the position of the central claw, the surgeon must use both hands to hold the retractor in position, loosen the wing bolt, move the central claw and then hold the central claw in position while tightening the wing bolt. In addition, the clearance passage through the central claw limits the range of longitudinal motion of the central claw. As will be apparent, it will not be possible to move the central claw to a position at which the clearance passage aligns with the wing bolt. If such an alignment occurs, the central claw will detach from the retractor. Moreover, the central claw clamps to one of the arms thereby fixing the angular position of the central claw relative to that arm. If the surgeon adjusts the arm separation, the central claw will move with that arm in a fixed angular relationship. Consequently, the central arm will not be equiangularly spaced from the two arms without repositioning the central claw as described above. What is needed is a scissors-type retractor that a surgeon can operate with one hand even when attaching or manipulating a central claw and that maintains equiangular spacing between the central claw and the retractor arms even as the surgeon changes the separation of the retractor arms.